gistfile1.php

<?php

$pkcs12file = new SplFileInfo(__DIR__.'/passbook.p12');

if(!file_exists($pkcs12file)) {
    $pkcs12 = new Pkcs12();

    $file = new SplFileInfo(__DIR__.'/passbook_certificate.pem');
    $certificate = new Certificate($file);
    $pkcs12->setCertificate($certificate);

    $file = new SplFileInfo(__DIR__.'/passbook_key.pem');
    $privateKey = new PrivateKey($file);
    $pkcs12->setPrivateKey($privateKey);

    $file = new SplFileInfo(__DIR__.'/AppleWWDRCA.pem');
    $certificate = new Certificate($file);
    $pkcs12->setChain($certificate);

    $pkcs12->exportToFile($pkcs12file);
}

$pkcs12 = new Pkcs12($pkcs12file);
$manifest = new SplFileInfo(__DIR__.'/manifest.json');

$signature = Pkcs7::signWithPkcs12($manifest, $pkcs12, PKCS7_BINARY | PKCS7_DETACHED);